Semiconductor lasers with a power of greater than 1 watt are generally lasers of the broad stripe type and, depending on the required emission power, may be unitary lasers or lasers arranged in parallel to form arrays. The main drawback of such lasers is that the amplitude distribution of their emitted beam in a plane perpendicular to their emission face is highly divergent (with a divergence of around 15° in a plane parallel to the active layers) and very inhomogeneous. This results in a reduction in the efficiency of coupling to an optical fiber. The cause of this is the existence of parasitic modes in the laser cavity and the presence of “filamentation” defects (the electron current within the semiconductor does not pass through the entire active section of the semiconductor, but inhomogeneously).
To improve the homogeneity of the near field of the emission face of such lasers, a monomode narrow stripe laser (acting as a filter), extended by a flared part acting as an amplifier, is integrated on the same chip. Power levels substantially above 1 watt can then be emitted, while maintaining a monomode transverse beam. The known lasers have been produced in the following two configurations. The first consists in etching, in active layers, a narrow monomode stripe with transverse index guiding followed by a flared part, which also has transverse index guiding, where “transverse index guiding” means that the lateral confinement of the optical field is achieved by differentiation of the refractive index between the narrow stripe zone and the zones bordering the stripe. The second configuration also includes a narrow monomode stripe with transverse index guiding, but followed by a flared part with transverse gain guiding. Hitherto, no other configuration has been proposed, as it was considered that only the two aforementioned configurations allow the quality of the laser beam emitted to be easily controlled. However, these known structures are relatively complex to produce and their dissipated heat is not easy to extract. For example, patent US 2004/125846 discloses a laser of the narrow stripe type, said stripe being extended by a flared part, but this laser is complex to produce (it includes etching and regrowth steps).